Geographic Range

The great-tailed grackle, Quiscalus mexicanus, was historically almost exclusively found in South and Central America, but human alteration of the environment has caused the birds to expand their range to include parts of the United States and Canada (Christensen, 2000). Their current range in the United States is north to eastern Oregon, with individuals sighted as far north as Canada (Sauer et al., 1997), south to northwest Peru, and as far east as Western Arkansas (Jaramillo, 1999).

Physical Description

The male great-tailed grackle is a large blackbird that appears purple-glossed. He averages approximately 45 cm in length and has a long ample tail. A potential identification problem exists between the boat-tailed grackle and the great-tailed, but the tail of the great-tailed tends to be wider and longer. The female is brown with a pale breast, and averages 35 cm in length. Both sexes have distinctive yellow eyes as adults (Peterson, 1990).

Development

The female of the species incubates the egg for 13-14 days. The chicks are born immobile, downless, with their eyes closed, and need to be fed by a parent. (Altricial development). The young leave the nest after a period of 20 to 23 days, and the female tends to them. (Sibley 2001).

Reproduction

Early in the spring males establish small territories and begin the process of attracting females. The breeding is polygynous, and the females nest in the territory of one male. Several females will nest in a single male's territory, and mate with him. First year males are excluded from breeding but young females are not. The main display is the "ruff-out" which is accompanied by a song. In the "ruff-out" the tail is fanned while the body feathers are ruffed and the head is arched upwards as it sings. The wings are drooped and quivered or held out towards the sides. The male courtship display differs in that it is more exaggerated, the bill is pointed down rather than up, and the wings are rapidly quivered while the bird produces distinctive "cheat" notes. The female may respond by drooping and quivering the wings as the tail is cocked and gives "che" calls. (Jaramilo 1999)

First year males are excluded from mating, but young females (1 yr.) are not (Jaramillo, 1999). The breeding season begins in early April. Nesting occurs in colonies of few to thousands, with the nests placed close together. The males tend to avoid confrontation with low key disputes. The females will fight over the choice of nest sites, and will steal nest building materials from one another. Clutch sizes tend to average 3 to 4 eggs, and females incubate them for 13 to 15 days. The young are born altricial and leave the nest at 20 to 23 days (Harrison, 1978).

Communication and Perception

Food Habits

The great-tailed grackle is known to eat insects, lizards, aquatic invertebrates and vertebrates, fruit, grain, and grass seed (Sibley, 2001). They are also known to remove and eat ectoparasites from livestock. Male nestlings appear to require more food than females of the same age (Ehrlich et al., 1988).

Economic Importance for Humans: Positive

May aid in agricultural pest control.

Economic Importance for Humans: Negative

Adult males are nearly granivorous (Jaramillo, 1999)

Negative Impacts

crop pest

Conservation Status

Over the past 30 years the great-tailed grackle has expanded its range in the U.S. at a rate of greater than 2.5% annually. This expansion is due to human modification of the landscape. Irrigation in arid areas, urbanization, and increasing cropland have all contributed to this expansion of range.(Christensen 2000)

Contributors

Patrick Koby (author), University of Arizona, Todd McWhorter (editor), University of Arizona.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

Neotropical

living in the southern part of the New World. In other words, Central and South America.

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

References

Christensen, A. 2000. "The Fifteenth- and twentieth-century colonization of the Basin of Mexico by the Great-tailed Grackle (Quiscalus mexicanus)" (On-line).
Accessed
March 2, 2002
at http://www.blackwell-science.com/geb.

Ehrlich, P., D. Dobkin, D. Wheye. 1988. The birder's handbook : a field guide to the natural history of North American birds. New York, NY: Simon and Schuster.

Harrison, C. 1978. A field guide to the nests, eggs, and nestlings of North American birds. Cleveland, Ohio: W. Collins Sons and Co..

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.